


given these parameters

by parsnipit



Series: flashpoint [4]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Angst, Hurt/Comfort, Implied/Referenced Torture, Injury, M/M, Protective Grillby, Trust Issues, Violence
Language: English
Status: Completed
Published: 2020-01-27
Updated: 2020-01-27
Packaged: 2021-02-27 14:34:26
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,063
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22428673
Author URL: https://archiveofourown.org/users/parsnipit/pseuds/parsnipit
Summary: When monsters break into the Core, Dr. Gaster is sent to defend it—it is, after all, one of the few things in the Underground the king values more than Gaster himself, and the consequences for failing to defend it are steep. Fortunately, Gaster isn’t fighting alone. Grillby’s much too stubborn to let him.
Relationships: W. D. Gaster/Grillby
Series: flashpoint [4]
Series URL: https://archiveofourown.org/series/1574302
Comments: 4
Kudos: 52





	given these parameters

**Author's Note:**

> warnings: violence, injury, references to torture

“Given these parameters, it simply isn’t reasonable,” Gaster says, scowling. “Compacting that much determination into that small of a space is impossible at best and overwhelmingly dangerous at worst. Perhaps if I had more time—”

Asgore snorts, leaning back in his throne and studying his claws. “I’ve asked the impossible of you before and you managed it just fine. You don’t mean to tell me you’re growing foolish in your old age, now, do you? I’d hate to have to replace you.”

“Foolish? No. More reasonable? Yes. There’s too much to lose if we try this.”

“You? What do  _ you  _ have to lose, Gaster?”

His mind flickers to fire, to the color purple, to gold jewelery and gleaming black teeth and the smell of smoke. “My home,” he spits. “My things, my money, my fancy clothes,  _ good food.  _ I’m not interested in blowing up half of the Underground this year, but thank you for the offer, sir. Try me next year.”

Asgore sits up, some of the amusement fading from his face. Gaster’s soul twists uncomfortably. “Now, now, I understand your reluctance. But surely you don’t mean to  _ actually  _ deny me this, do you? After all—”

The doors to the throne room burst open. Asgore and Gaster both snarl and bear their teeth, their eyes snapping back towards the doors. A small goblin trembles in the entryway, their armor dulled by dust and dark blood. “There’s been a break-in, sires,” it says, panting. “Monsters from the slums, lots of them, they tore through our defenses, they—”

“Where?” Asgore demands, standing. His shadow falls over Gaster, the light glinting dangerously off of his horns. 

“The Core, sire.”

Gaster goes rigid. The Core.  _ His  _ Core. Fuck. He has to go, he has to leave right now, no one can touch the Core,  _ no one can damage the Core— _

A fine, frantic rattle begins to worm its way through his bones. He can’t hold still.

“Dismissed,” Asgore says sharply to the goblin. “Back to the fight with you. I’ll send reinforcements shortly, but by the gods, don’t you dare let anyone else in. If the Core is damaged in any way, I’ll see to it everyone in this battle is slaughtered—and that  _ includes you.”  _

The goblin bolts. Gaster’s hands shake. He shouldn’t be standing here, he should be gone, he should be in the Core already, he should be wicked teeth and blazing eyes and blasts for anyone who dares to fucking  _ look  _ at his creation with intent to harm. That’s his duty. The alternative is unthinkable. (He knows he won’t survive it a second time.)

“Oh, look at you, pet,” Asgore says, his voice warping into a croon. He rests one massive paw on Gaster’s skull, and Gaster shudders. “Already ready to go, aren’t you? Now, as much as I value that clever mind of yours, we both know the Core is worth more. Where would we be without it, hm? It’s yours to defend, my dear—and if a single  _ bolt  _ is out of place when I arrive, I will strap you down and strip the marrow from your bones, and I’ll do it nice and slow. Understand?”

“Yes, sir.”

“Good. Now  _ go.”  _ His voice is a snap of command, and Gaster moves before he thinks—his mind is nothing but a blur of red and a high, panicked hum. He jumps through spacetime and lands in the core of the Core and finally, finally lets himself shake with all the fear churning in his soul. Oh, gods, he doesn’t want to do this. He’s so frightened. What happens if he fails, he can’t go through that again, he can’t fail, he can’t, he can’t he can’t he can’t not again  _ not again please not again _ —

Then he hears a scuffle of noise and he whips around, rolling his jaw back into its second hinge and bristling his vertebral spines. His fear vanishes, replaced by desperate focus. He knows his duty. He knows it very well, and he dares not fail—so he prowls forward, a low growl humming in his chest, and he gets to work.

***

Grillby growls, ramming his shoulder against a locked door. The metal creaks, but it doesn’t budge, and Grillby bares his teeth at it in infuriated frustration. The second he’d heard that the Core was under attack, he’d bolted for Hotland. He didn’t even bother closing the bar—who cares if his patrons steal from him, right now? A building can be remade, money can be re-earned (or, as the case may be, stolen  _ back),  _ alcohol can be rebrewed, but Gaster? Gaster can’t be brought back to life, if Grillby lets him die. 

So here he is, carving his way deeper and deeper into the Core, searching desperately for his partner—and here this door is, trying to stop him. Unacceptable. He steps back, lifts his foot, and slams it into the door’s control panel. At the same time, he pushes a blast of fire forward with his heel, forcing it deep into the panel’s casing to warp wires and melt through its alarm system. With a defeated wheeze, the door unlocks, and Grillby shoves it open.

As soon as he does, a pair of guards turns on him. Shit.

A werewolf lunges at him first, crooked yellow teeth bared and claws outstretched. He springs to the side and she skids past him—as she does, he reaches out and drags his fingers across her flank. The metal of her chainmail flashes bright-hot. He smells smoke and broiled flesh as it warps into her side, and she shrieks and whirls around, clawing desperately at his arm. Her claws take a few inches off of his core, but it’s barely a sting, and nothing that won’t reform within the next few minutes.

He moves on to his next victim.

This one is a centaur with a bright blade—Grillby has to take care not to be struck by the first heavy-hoofed kick he’s offered, but that kick opens the centaur’s belly to him for a few precious seconds. He darts underneath its hind hooves, smoothing his palm across its stomach in a macarebe mimicry of a stroke. Delicate skin crisps and blisters in his wake, and the centaur shouts and brings its sword down as soon as it has all four feet on the ground again. The blow is weak, clumsy with pain, and easily dodged. He whirls to face the centaur once he’s a few feet away, raking a hand through the air in front of him. A streak of fire blooms out in the air in front of his fingertips, slashes its way across the centaur’s face. The centaur rears, shrieking with pain and churning the air with its hooves. 

Oh, would you look at that? The werewolf’s back for more. She just can’t get enough of him, can she? He can’t blame her. He’s  _ quite  _ the ladies’ man.

Grillby backs away from the centaur—he’d rather not be struck by a stray hoof, please and thank you—and bristles his flames in warning. The werewolf flattens her ears warily, licking her lips, and the two of them circle each other for a few brief, uncertain seconds. Grillby decides quite quickly that he doesn’t have time for this. He slams his heel into the ground and a line of fire sprouts up along the ground in front of him, surging towards the werewolf. Her eyes widen and she stumbles away from it. When she does, Grillby turns his foot to the side, and the line of fire follows suit, chasing her down. She springs forward, and the second she does, Grillby drives his hand forward, and with it, another blast of fire. This one hits her squarely in the chest, and she staggers backwards with a cry of pain. When the smoke clears, she looks on him in terror, and does not move again.

He leaves the guards behind to suffer their injuries, darting into the next hallway. As fun as fighting is, he has bigger priorities. Gaster’s only ever brought Grillby to the Core once, but if he’s remembering the layout right, he thinks he’s almost to the center. His suspicions are confirmed when, the second he breaks his way through another sealed door, a blaster pounces on him. Heavy paws slam him into the ground, and the blaster screams at his face. Gaudy red magic builds in the back of its maw. 

Well, fuck.

The blast hits him, and he takes a deep breath and lets it wash through his flame. He absorbs as much of it as he can into his core, although there’s far too much of it for him to avoid any injury. The force of the magic chips away at his forearms where he crosses them in front of his face, and he hisses in pain as his core crumbles off. The blast dies away after a few seconds, and the blaster stands over him, panting anxiously and looking quite baffled to see him still alive.

“Hey, buddy,” he groans. “Nice to see you too.”

The blaster opens its jaws again, a low whine cresting in its chest.

“Oh, no, nope nope nope nope, playtime’s over—” Grillby pushes both hands forward, and a ball of fire pushes the blaster off of him and sends it skidding across the floor, although it manages to stay on its feet. It digs its claws into the ground and clicks its lower jaw irritably at him, stalking forward again. “What’s got you so worked up, huh? You know me. Let’s just—”

The blaster leaps. Grillby yelps and darts out of the way.

“Dings!” he shouts, because where there is a blaster there is a skeleton nearby. “Dings, call off your dog!  _ Dings—” _

The blaster swipes at him, and this time, he doesn’t quite scramble out of the way in time. Its paw sends him flying into the nearest wall, and he thuds into it with an  _ oof.  _ Jesus. He should have brought treats or something. 

“Okay.” He straightens up, bracing a hand against the small of his back.  _ That’s  _ going to be sore for a while. “I really don’t wanna hurt you, bud. Let’s just chill out.”

The blaster shakes its head, the heavy chain collar around its neck jingling as it does. Grillby sees the light flash off of its tags—off of the  _ king’s emblem _ on its tags—and his soul sears with a sudden flash of anger. It stalks forward again, its head low and its tail flicking.

“Listen. I know this is your job,” he says, trying to keep his voice calm, “and I’m not here to stop you. I’m here to help you. You know I wouldn’t do anything to put you in danger.” He raises his voice, shouts to the Core.  _ “You know that, don’t you, Dings?” _

The blaster springs again. It slams him into the floor, red magic trailing from the corners of its mouth. It hisses, low and frustrated, and then—

“What,” Gaster demands, his shoes clicking on the floor as he crosses it, “the  _ hell _ are you doing here?”

“I came to save you. Your knight in shining armor, huh?”

Gaster groans. Grillby tips his head back to see Gaster standing a few feet away, rubbing the bridge of his nose. “You know what? I should let her eat you.”

The blaster chatters her teeth in approval.

“C’mon, you’d miss me,” Grillby teases. He pats the blaster’s leg, cooing at it, “Wouldn’t he? Wouldn’t he miss Daddy? You’d miss Daddy, wouldn’t you, big girl? Can you get off of Daddy? No? Just gonna stand there? You’re just—you’re just a little bit heavy, that’s all—”

Gaster groans even more dramatically and snaps his fingers. The blaster steps off of him, crouching a few feet away. “I don’t have time for your games right now, Grillby. You shouldn’t be here.”

“I know, I know.” Grillby sits up, rubbing his sore forearms. 

Gaster watches him with vaguely-masked concern. “Did she hurt you?”

“Not badly. It’s alright. What about you? Are you hurt?”

Gaster glances away. “No. Anyone who’s gotten this far has been taken care of.”

“Are you sure?”

“Yes, Grillby,” he says, sighing heavily. “I’m sure.”

“Well, in that case—” Grillby clambers to his feet, shaking himself off. “Let’s get to work!”

Gaster grumbles and complains, but he doesn’t drive Grillby away, and for that, Grillby can only be grateful. The two of them fight side by side for another couple of hours, although few monsters make it to the Core’s core—and most of them are heavily wounded by the time they do. Gaster’s blaster makes quick work of them, and the one or two who manage to eek by,  _ Grillby  _ deals with. Gaster grouches about that, for the first hour, and then he gets...quieter, more content to sit against the wall and watch Grillby fight.

It’s concerning, to say the least.

Asgore comes to speak to them, once the intruders have been driven off, and Gaster grows even quieter and meeker. He keeps his eyes down and his shoulders low, and his blaster’s tail curls between her legs. Grillby simmers with rage, but he dares not speak—not yet, not now, not in front of the king who terrifies Gaster so very much.

He is more than grateful when they’re both released, and he and Gaster make a beeline for Gaster’s house. Grillby groans, stripping off his dust-spattered clothes as soon as he can and tossing them into Gaster’s laundry hamper. He hates dust. He hates  _ clothes— _ mm, but they do make him look handsome.

“Put something on,” Gaster chides. “You’ll get cold.”

“What? Don’t you like the view?”

Gaster doesn’t rise to the bait. Instead, he curls up on the bed. 

“Dings?” Grillby tugs on a pair of sweatpants before leaning over Gaster, his brow furrowed. “Don’t you wanna change? Or, like, shower? No offense, but you’re pretty gross right now.”

“Later. I’m tired now.”

“Blaster took a lot out of you, huh?”

“Mm-hm.”

Grillby takes a seat on the bed, resting a hand on Gaster’s shoulder, and Gaster—flinches. Grillby’s stomach feels tight. “Dings. You’re sure you’re not hurt?”

...there’s no response, this time.

“Dings? Fuck. Fuck, let me see, take your shirt off—”

“Don’t touch me.” Cold, sharp. Grillby jerks his hands back. “I’m fine.”

“You’re not fine! You’re  _ hurt.  _ Let me see, let me help—”

“I don’t want your help.”

“What’s wrong? Why not?”

“I just—I don’t—” Confusion flickers across Gaster’s face. “I—I—”

“It’s because Asgore frightened you, isn’t it?” Grillby’s hands ball into fists. “I’m not him. I’m not  _ ever  _ going to hurt you like that, Dings. I will not  _ ever  _ hurt you when you’re weak and scared. You know that.”

Gaster is silent.

“You know that, right?”

Red eyelights flick guiltily away from him.

“Dings.” Grillby’s soul aches fervently. He takes a deep breath, and it leaves him in a curl of miserable, dark smoke. “...damn.”

“I’m sorry.”

“It’s not your fault.”

“I wish I wasn’t this way.”

“I know.” Grillby stands, rubbing the back of his neck. “I’ll go into the living room. Clean yourself up, okay? Let me know when you’re done.”

He leaves Gaster to lick his wounds in the safety of solitude. Once he’s in the living room, he flops down on the couch, grabs a pillow, and shrieks his absolute fury into it. His flames lash, but he does his damned best to keep them from burning any of Gaster’s precious possessions. How  _ dare anyone  _ make Gaster feel this small and frightened.  _ How fucking dare they.  _

...Grillby thinks about killing the king, again.

After a few minutes, he hears the soft click of bone as Gaster moves into the living room. “Grillby?”

“Hm?” Grillby glances up from one of the incomprehensible textbooks he’d been browsing, cocking his head. Gaster’s cleaned most of the dust and blood from his bones, and now that he’s shirtless, Grillby can see the cracks lacing through the ribs on his right side. Further down, where Gaster’s sweatpants hang loosely on his hips, Grillby can just barely make out a crack along the arch of his hip, too. He winces in sympathy. “Ow.”

“Yeah,” Gaster says quietly. “Can you help me bandage my ribs?”

Grillby stares at him. “What.”

“Can you help me with the bandages?” Gaster hunches his shoulders, casts his eyes down. “...please?”

Grillby scrambles immediately to his feet, absurdly giddy. Gaster is going to let him help? Gaster is going to trust him with these wounds? Stars, he shouldn’t be getting this excited  _ but he is.  _ “Yeah—yeah, of course I can, baby boy. Here, come here.”

He leads Gaster to the bathroom and scoops him up, setting him down on the counter. Gaster braces his hands against Grillby’s shoulder, for whatever semblance of control that gives him. Grillby rummages through their first aid kit, pulling out antibiotic ointment first. “Can I put this on?” he asks, showing Gaster what he has.

“Yes, that’s fine. Be—” Gaster winces, bares his teeth in a grimace.

“Be what?” Grillby studies him. When Gaster doesn’t respond, he hazards a guess and responds, “I’ll be gentle. Don’t worry. I don’t want to hurt you.”

Gently, as gently as he knows how, Grillby dabs antibiotic ointment across each fracture. He pauses to rub his thumb lightly across the crack in Gaster’s hip, humming unhappily as he smooths out the ointment. Once that’s done, he plasters a bandage over Gaster’s hip, then gets to work winding a much larger bandage around Gaster’s ribs to brace them. The entire time, Gaster keeps a vice grip on his shoulders, ready to push him away if it hurts too much—but he never does. For Grillby, the progress feels enormous.

Things are far, far from perfect—but this, right now, this tiny moment of trust? It’s something Grillby is going to cherish for as long as he can. He knows, however, that Gaster is never going to be  _ okay.  _ He’s never going to belong entirely to Grillby. He’s never going to feel completely safe—not, at least, until the king is dead.

Grillby can’t kill the king (not yet), but he can patch up the wounds that bastard’s left and hope hope  _ hope  _ there won’t be any others for quite some time.


End file.
